(+3又 3/4)-(-1又 1/2)+(-1/6)-(-5/8)+(+4又 2/3) =3 又3/4+1 又1/2+5/8+(4又 2/3-1/6)= 3又 3/4+5/8+(4又1/2+1又 1/2)=4又3/8+6=10又3/82-(5又 5/6)-(4 又3/7)+(-2 又1/6)-(6又 11/21)=2-(5又5/6+2又1/6)-(4又3/7+6又11/21)=2-8-10又20/21=-16又20/21